These are going to be good tubes in the Mk III based on my experience; I used a pair of similar vintage in my Integrated and then in my Torii for some time. Will have a darker, punchier sound than the stock tubes. In my experience the fifties and sixties share a family sound. The fifties may be a bit more revealing of fine detail than the sixties of tubes I've had, which may or may not be a good thing. . . .

I agree with Lon's assessment. I have some RCAs that look just like these, and they are the darkest of my Rectifiers, of which I have many. Last I listened, these were also my least favorite, though I should try them again.

I tend to like the inner detail and spaciousness from the tall bottle 5U4G-B shape. May be coincidence, but all that I have share this quality in different ways. And there is something about those 40s and 50s tubes too, though I really like some later ones as well.

So if these are a little dark, you might check ebay for some tall bottles. Haven't checked lately, but I bought a bunch over time very inexpensively. And actually, the Rectifier for me seems to be a primary rolling tube these days for fine tuning.

Lately I am enjoying some 50s Svetlana Winged C 5U4G-STs, tubes I did not like at first, even after quite a few hours of burnin. I think it is synergy with the set I am using, but also, I think mine were actually new tubes and they took a while to clarify and balance (I guess 70-80 hours).

Thanks for sharing will. I'm not looking for dark (just came from there). I'm looking for something to take a bit of the edge off. The amp has around 500 hours on it. Stock tubes, except for Treasures and it has the VCAPS.

Seems like you are over the edge on the Treasure burnin, and maybe over the hard part of the Vcaps by most reports, but I think a range of 5U4Gs is not a bad idea, broken in caps or not. But then I am a tube roller.

A lot of tubes will soften the edge a bit. Guessing the RCAs you have are doing that??? Question being, is it too far for your tastes...too dark and/or too much density? Do you like them, or how would you change them if you could?

I'm not really interested in tube rolling at the present time, however I do want to swap out the stock Rubys. The RCA's appear to be most popular, so I'm just trying to decide on which model/vintage and a recommended place to buy.

Or if you don't have the RCA reference, would less edgy than the Rubys be your only criteria... Like would you prefer warmth, or neutrality...Some Raytheon and Tungsols have some really nice smooth, warmth without detail sacrifice.

My idea of "warmth" is having a darker thing happening compared to "neutral" but with natural and smooth detail to allow an inner spaciousness and texture. Warm feeling without leaving a sense of dark/restricted/ closed.

I am listening to Ruby's now with some quite warm early 60's Amperex 6922 SQs, and it sounds great to me, the Ruby's bringing in some nice openness to these inputs that tend a little to heavy warmth for me.

I don't have any typical tall bottle RCA's, but have found tall bottles less dark/more open than short. It is possible this is based somewhat on the coincidence of the individual tubes I have, but I definitely see this pattern in my rectifiers. The tall RCA 5U4GB's I do have, I believe may be from the early 50s. They are extra tall with the internals are like RCA 5U4G-STs. These tubes are open, extended, smooth, and have a lot of finesse. They are on the brighter side of the range, but not as bright seeming as the Ruby...being notably smoother with this tube set.

I see no reason to pay high for rectifiers if you can find what you want on Ebay. And if the tubes test good and match, I don't care if they are NOS, in fact being glad to have them broken in. I do look carefully to see that they are the same construction...same getters, bottles, plates...etc.

Anyway, if you give me a good description of how you would change the Ruby, I can suggest some tubes that I think would go there.

"My idea of "warmth" is having a darker thing happening compared to "neutral" but with natural and smooth detail to allow an inner spaciousness and texture. Warm feeling without leaving a sense of dark/restricted/ closed".

I just moved from a vintage Scott 299, which is quite dark. The Torii is quite different and I am learning to love it with each play. That being said, I listen to quite a bit of classic rock and find the amp to be a bit bright at volume for those types of recordings, so I guess I'm looking for a bit of warmth. I'm not interested in tube rolling at the moment, but would like to replace the Rubys and let the amp continue to break-in...if that makes sense.

Being cheap, and offering different tonal characters, I think you might do well to pick up both of these. They are not exactly like the tubes I have but quite close in construction and the same companies. I suspect (hopefully!@#$%^&*) close enough to anticipate similar sound. I think the Raytheon will be warm but rich, and the Sylvania more open like the Ruby, but more refined....a bit warmer, richer, and smoother. The 3rd link, the Tungsol is closer to the Raytheon, on the warmer side, another good looking tube.

My system/room and ears, and synergy between tubes is real and can create some anomalies, but I think these will chill down the edge you are experiencing.

Thanks for taking the time will. I'm familiar with all 3 auctions. I've been hunting and just trying to decide which way to go and your feedback is a great help. It's a fun and interesting hobby. I'm learning quickly that the same model tube can sound completely different in the same model amp, depending on tube mix, listening room, etc, etc, etc. I'm starting to understand why people tube roll. It's about experimenting and finding the mix/combination that is to one's liking. Cheers

Yes I think that is the tube rolling thing...it gives you a way to fine-tune to your tastes within the givens of your system/room.

But I think there is comparative reality. If we both have MK IIIs...then comparing the nature of one particular tube within one tube type, with another tube of the same type...you can get relatively clear about the attributes of those tubes, and how the tube's characters compare. That is if you keep a baseline of all other tubes, adjustments and the rest being left the same during the comparison.

I hope you find something that sounds good to you. It is a lot of fun!